1. Field of the Invention
The present invention relates to minimally invasive surgical instruments, and more particularly, to instruments having a linkage mechanism and assembly for enabling an end effector, such as jaws of a surgical forceps, to move between an open and a closed position in parallel relationship to each other.
2. Description of the Prior Art
Laparoscopic procedures have been developed relatively recently as a less invasive alternative to traditional open surgeries. Numerous surgical procedures, such as gall bladder operations, are currently performed by laparoscopic techniques. These surgeries are generally termed "minimally invasive surgery" (MIS) and the present invention refers to a class of devices that have rigid shafts with hand-operated handles at one end and an end effector mechanism (such as jaws) at the other end. End effector mechanisms refer to the portion of the surgical instrument that actually contacts and manipulates tissue in a patient. The prior art of most concern herein relates to grasping forceps, which grasp but do not intentionally cut or puncture tissue; for example forceps with broad jaws are use for tasks such as pulling out gall bladders that have been surgically cut away from the liver. These devices replace the surgeon's hands in the traditional open surgery. However, prior laparoscopic grasping devices often may cause problems in their inability to properly grasp the object, such as a gallstone. The lack of satisfactory holding power of these instruments can complicate the surgeon's work. Tissue that must be manipulated during a surgical procedure can have widely varying surface characteristics and can be highly slippery and difficult to grasp. Additionally, such prior devices lack the necessary holding power, thereby forcing the physician to exert significant grasping pressure in order to manipulate tissue as required to perform the surgical procedure. Use of such high grasping pressures can result in increased long-term trauma to the tissue.
The typical instrument employed in laparoscopic surgery has a hollow clindrical shaft, which includes a solid actuating rod. The rod is connected at the distal end to the effector mechanism (jaws), and at the proximal end to one member of the handle assembly. When the handle is operated, the rod slides through the shaft and actuates the end effector mechanism. Serrations and other features (depending on the use for which the instrument is intended) enable the end effector to perform various surgical functions, such as gripping.
Many creative linkages have been devised for converting the surgeon's manual efforts, at the handle end of the instrument, into opening and closing of the instrument's jaws. Typically, although with some exceptions, the handle has a stationary member rigidly joined to a hollow shaft and a movable member pivotally joined to an actuator rod that is mounted and is capable of reciprocal movement within the shaft. When the surgeon squeezes the stationary and movable handle members together, the actuating rod acts upon the jaws (to which it is rotatively fastened by pins, or by tracks of levers kinematically equivalent to pins) in such a way as to make the jaws close. When the surgeon spreads the stationary and movable members apart, the movements are reversed and the jaws open. The jaws are usually attached to the end of the shaft by known means, e.g., by pins or kinematically equivalent tracks. In some cases, levers or other intermediate pieces are interposed between the actuating rod and the jaws for causing the latter to open and close in response to relative movement of the stationary and movable handle members.
When operating the jaws of typical instruments as described above, surgeons have experienced difficulty in grasping slippery tissues because the jaws close first at their rear ends, and thereby tend to propel or push the tissues out from between the jaws. This is illustrated in FIG. 1, which shows that when attempting to grasp a relatively large object, the rotary force tends to push the object out of the jaws as well as hold it. Consequently, trauma of the tissue may result from repeated and increasingly aggressive attempts to grasp the tissue.
Laparoscopic instruments intending to simplify operative treatment on a tissue are known in a large number of variants, particularly when designed as a grasping instrument. Thus U.S. Pat. No. 5,318,589 issued to Lichtman on Jun. 7, 1994, teaches of a surgical instrument having jaws opening and closing. This patent is typical of a class wherein the jaws are normally biased in one position, then moved in response to the squeezing motion of the handle assembly. There is no independent linkage to control the jaws, therefore these jaws will have a tendency to lack grasping power.
U.S. Pat. No. 5,728,121 issued to Bimbo et al. on Mar. 17, 1998, discloses a surgical gripping wherein the grasping jaws employ a gripping material for enhanced holding power. The jaws themselves have a conventional means for movement.
U.S. Pat. No. 5,368,606 issued to Marlow et al. on Nov. 29, 1994, illustrates a means of actuating the jaws by a linkage method of manipulation. The method falls short of teaching a means for opening and closing the jaws in parallel relationship to one another.
U.S. Pat. No. 5,853,412 issued to Mayenburger on Dec. 29, 1998, teaches the use of toggle lever elements to move the jaws. No disclosure is made as to moving the jaws in a parallel relationship to each other.
U.S. Pat. No. 5,308,358 issued to Bond et al. on May 3, 1994, discloses a double-motion actuator assembly which comprises a linkage means, but not a teaching of parallel movement between the jaws themselves.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.